While lumber and other wood based products derived from trees are not perishable, they are, nevertheless, susceptible to a host of natural destructive forces. These primarily include attack by insects, such as termites, carpenter ants and the like and fungi such as brown (Poria Sp.) and white (Polyporous Sp.) wood decay fungi (Poria Incrassata). Living, growing trees are also subject to attack from insects and fungi.
Many protective treatments have been developed for the protection of lumber and other tree derived products. For example, Bechgaard, U.S. Pat. No. 4,610,881 relates to a protective composition with a penetrating carrier which comprises a mixture of ethylene glycol and a borate-containing composition which may be disodium octaborate tetrahydrate. In addition, the composition may be diluted with up to 50% by weight of water. However, the Bechgaard patent specifically teaches that such additions of diluent are disadvantageous because aqueous solutions of the active ingredient diffuse into the wood more slowly. Therefore, the amount of dilution should be minimized and, in fact, should not exceed 20% by weight. In fact, Bechgaard instructs that it is preferred that no water be present, to the extent possible. Bechgaard also suggest that it is known to impregnate wood with polyethylene glycol in order to make the wood more dimensionally stable (preventing shrinkage when the wood dries). See also Ember, Preserving The Past, C&E News 10, 12 (Nov. 14, 1988). It has also been suggested that minor amounts (i.e. about 2%) of fungicidal, insecticidal or fire retardant agents may be added thereto. These additives can include boron containing compounds. See Ember, Preserving the Past at Page 12. However, such uses involve polyalkylene glycols having a relatively high molecular weight, i.e., 1000 or higher.
Chapman et al. U.S. Pat. No. 3,305,298 relates to a protective treatment for wood. The treatment includes water, methanol, ethylene glycol, propylene glycol ethers, hologenated phenols, soluble borates, appears to be used as a buffering agent for the system. Chapman et al. requires the formation of a complex compound involving the organic mercury compounds, the borate ion and the hydroxylated compounds.
Ploquin U.S. Pat. No. 2,968,590 relates to a synergistic boric acid fungicidal composition which includes a boron containing composition, at least one organic compound having in its formula two identical or different radicals selected from OH, NH.sub.2, NH and at least one organic or mineral base in an amount sufficient to make the pH of the product in the neighborhood of about pH 9. The organic compound may include "the glycols". All of the examples of Ploquin are limited to hexylene glycol or methylene glycol.
Stutz, U.S. published patent application B 848,336 relates to a wood preservative containing alkaline metal cyanides. More specifically, the alkaline metal cyanide is added to an alkaline borate buffered liquid fungicide concentrate of chlorophenates, and organic or inorganic salts of mercury, lead, titanium, copper and zinc. Furthermore, Stutz discloses the use of solvents which consist of alkanols having 1-4 carbon atoms which include a number of glycols identified at Column 2, lines 50-54.
Thornton et al., British Patent No. 937,766 relates to improvements in the treatment of wood and in the products obtained. The patent discloses a formulation which includes a boron containing active ingredient mixed with a small amount of a glycol containing from 2-8 carbon atoms, especially ethylene glycol. The amount of such ingredients should not exceed approximately 5%. Ethylene glycol, as used in the practice of the patent, is shown to be effective in concentrations of approximately 1%.
Short et al., U.S. Pat. No. 4,076,871 relates to a method of impregnating wood with boric acid or boric oxide by the use of boric acid esters of alcohols and thereafter hydrolyzing the esters. According to Short et al., it is well known that boric acid or boron oxide are effective as flame-proofing and fire-retardant agents for wood products.
See also, generally, Birkner et al., U.S. Pat. No. 3,099,598, Draganov, U.S. Pat. No. 3,378,381, Patel et al., U.S. Pat. No. 4,719,110, Goettsche et al., U.S. Pat. No. 4,761,179, Turner, U.S. Pat. No. 4,303,726, Boocock et al., U.S. Pat. No. 4,440,298 and Oberley, U.S. Pat. No. 4,373,010.
However, despite these and other wood preservative products and methods, nothing has been found to be completely satisfactory for a variety of reasons. For example, the composition of Champman et al. and Stutz include such compounds as alkaline metal cyanides and organic or inorganic salts of mercury. Such compounds are environmentally hazardous, many pose safety risks to persons and animals, and create difficult and expensive disposal problems.
The composition described in Bechgaard does not appear to suffer from these disadvantages. However, the viscous ethylene glycol solutions taught therein are not applicable to all situations and not suitable for a number of application techniques. See Johnson et al., A Test of "Boracol", A New Formulation Containing Borates, For the Diffusion Treatment of Lumber, project No. 02-17-43-396 dated May 1986, prepared for Forintek Canada Corp. at page 1. Furthermore, testing has established that the compositions of Bechgaard are not effective in either rapid or deep penetration. See Id. In fact, it has been found, completely contrary to the teachings of Bechgaard, that the presence of water in a borate delivery system is generally necessary for reasons other than a reduction of viscosity.
Finally, all of the treatments previously described are limited to timber, lumber and tree derived products. They are not applicable directly to living, growing trees to protect them from infestation.